It is known to couple a LAN system in which computers are arranged to communicate with one another using one set of protocols to another LAN system of computers using a different set of protocols. Such set-ups necessarily employ software programs to enable signals to be transferred between the systems without violation of the respective protocols. The need for special software would also be manifest when transferring communications between two computer communications systems of the same type because each system has its own specific environment in which computer calls are recognized and services. It therefore follows that all such combined systems, needing software interfacing, lack transparency between their parts and any hierarchal structure would bring in train unmanageable complications.
The present invention is directed towards facilitating a hierarchal structure of computer communications systems, all operating within the constraints of token ring protocols, wherein at least one of the systems comprising the hierarchal structure has a core comprising a token ring hub as described and disclosed in our aforesaid copending application Ser. No. 177,764 and another one of the systems may be either a token ring LAN system or comprise a further token ring hub as aforesaid. Each such token ring hub is characterized by having means adapted to receive a signal indicative that the requirements of the standard token ring protocols are satisfied with respect to a computer connected directly or indirectly to the hub and in response to said signal to forward a comparable signal to the next system into which the hub is inserted in hierarchal succession. The latter signal is likewise indicative that the requirements of the intrinsic protocols are satisfied with respect to the connection of the hub per se into said next system. In the present context, a hierarchal connection is a connection which has the capability of at least one further connection to it so as to form one link in a possible chain of connections. Each such connection also facilitates one or more merging connection. "Transparency" in the present context means that the effect of a connection is to physically and electrically enlarge a pre-established token ring and the effect of a disconnection is to physically and electrically reduce the said token ring, all without any interference in communications proceeding between existing or remaining elements of the ring. When another system is connected in this way the elements of the other system may be communicated with as though they are pre-existing members of the ring into which they are added.
Thus it is an object of the invention to provide a computer communications system in which some of the parts have hierarchal relationships with other parts. It is also an object of the invention to provide a hierarchal system in which the parts are adapted to a token ring topology and may be coupled to a LAN computer communications system implemented as a token ring.
These objects and features of the invention are further described hereinafter by way of example and with reference to the accompanying drawings.